The present invention relates generally to dewatering elements for paper making machines and in particular to adjustable foil apparatus with a cam actuated adjustment means for adjusting the foil angle that a rigid foil body of ceramic or other hard wear resistant material makes with the conveyor belt carrying the paper stock over the foils in such paper making machine, without bending the foil body. The adjustable foil apparatus of the present invention is especially useful for paper making machines in which the foil angle is adjusted without removing the foil apparatus from the paper making machine and without stopping the conveyor belt of such paper making machines.
Previously it has been proposed in U.S. Pat. No. 3,027,940 of Dunlap, issued Apr. 3, 1962, to provide a foil apparatus for a paper making machine including a foil member having a bearing surface of plastic material mounted on a flexible metal sheet which can be adjusted by bending the foil. The angle of the foil is adjusted by bending the foil body in response to the amount of air pressure applied to the interior of two flexible hoses within the foil mount which cause the foil rear portion to move down against an adjustable stop. This has several disadvantages, including the fact that it is not suitable for use with rigid foil body members such as those made of ceramic or other hard wear resistant material, which are not flexible. Also, the adjusting mechanism is extremely complicated, requires uniform adjustment of stop screws, and is subject to failure if the inflatable hose is damaged or otherwise develops a leak.
Another type of flexible foil apparatus for paper making machines, whose angle is adjusted by bending the foil member is shown in U.S. Pat. No. 3,140,225 of Truxa, issued Jul. 7, 1964. This foil includes a plastic or other non-metallic cover member mounted on a spring steel support which is bent by the movement of pin projections with a sliding adjustment bar, which engage cam slots in the spring support mounting member. This has the disadvantage again that a long wearing foil having a rigid body member made of ceramic material cannot be employed, since such a rigid body is not flexible and cannot be bent to adjust the foil angle.
U.S. Pat. No. 3,201,308 of Goddard, et al., issued Aug. 17, 1965, and U.S. Pat. No. 3,220,920 of Truxa, issued Nov. 30, 1965, shows another type of drainage foil apparatus including a flexible foil member with a thin flexible neck portion which is adjusted by bending the foil with a cam actuated operating mechanism in response to lateral movement of a slide member in a similar manner to the previously discussed patent.
Adjustable angle foil apparatus including a flexible foil body member of plastic which is bent to adjust the foil angle is disclosed in other patents, including U.S. Pat. No. 4,162,937 of Corbelini, issued Jul. 31, 1979. In this foil, a nose portion at the front of the foil is made of a hard, wear resistant material such as stainless steel or ceramic, while the body portion of the foil is made of flexible material such as plastic which is bent for adjustment of the foil angle by rotation of an eccentric shaft coupled to the end of such rear portion of the foil. This foil apparatus is not suitable for adjustment of rigid foil body members.
It has also been proposed in U.S. Pat. No. 3,535,201 of Reynolds, issued Oct. 20, 1970, to provide an adjustable angle foil with a rigid foil body in which the entire foil member is pivoted by means of a complicated and expensive mechanism including a plurality of threaded bolts. This is difficult and time consuming since each bolt and a variable length link must be individually adjusted to move a support in an arcuate keyway at both ends of the foil to vary the foil angle. Another rigid foil apparatus with foil angle adjustment is shown in U.S. Pat. No. 4,061,532 of Biondetti, issued Dec. 6, 1977, in which the foil strip is mounted on a tubular carrier, which is pivoted by a leaf spring for adjustment of the foil angle in response to the adjustment of threaded screws. The foil angle adjustment screws have different thread pitches at the opposite ends thereof, which is extremely complicated and expensive to make and difficult to adjust. More recently, rigid foil apparatus with adjustable foil angles have employed even more complicated threaded adjustment means, as shown in U.S. Pat. No. 4,416,731 of Pesonen, et al., issued Nov. 22, 1983. U.S. Pat. No. 4,865,692 of Kade, et al., issued Sep. 12, 1989 shows a rigid foil with an adjustable angle provided by an inflatable hose and adjustable stops, which is somewhat similar to the above-discussed Dunlap U.S. Pat. No. 3,027,940. However, Kade adds the additional complication of a flexible hinge and a slide cam member with adjustable stop surfaces thereon for adjusting the angle of the foil.
All of the above prior adjustable foil apparatus suffer from the disadvantages that they are either restricted to flexible foil bodies, which are bent to adjust the foil angle, or to rigid foil bodies with an extremely complicated and expensive foil angle adjustment mechanism involving threaded adjustment screws, arcuate keyways, adjustable length couplings and the like, which are extremely difficult and time consuming to operate in order to produce accurate angle adjustments of the foil regiments uniformly along the length of the foil. These problems have been solved by the adjustable foil apparatus of the present invention, which is suitable for use on a foil member having a rigid foil body of hard, wear resistant material such as ceramic material, to provide a long wearing foil member which does not have to be replaced frequently and whose foil angle can be adjusted quickly and accurately with a simple cam actuated adjustment mechanism, in order to simultaneously adjust the angle of all of the foil segments along the entire length of the foil to the same uniform foil angle.
The adjustable foil apparatus of the present invention has several advantages over the prior foil apparatus, including adjustment through the required foil range of 0.degree. to 5.degree. with great precision in small angle increments of 5/100th of a degree, as well as in larger 1/2 degree increments in a precise manner. In addition, the foil angle can easily be adjusted while the foil is still installed on the paper making machine, without removing the foil or stopping the paper making machine. This has the advantage that foil adjustments may be made quickly while the conveyor "wire" is running to check to see whether the foil causes a streak in the paper, which indicates that the foil is damaged or of an improper height. This enables detection of any such problem in a fast and inexpensive manner without stopping the machine unduly reducing the paper production output.
The foil angle adjustment mechanism of the present invention is cam actuated to provide a simple and inexpensive adjustment mechanism which is fast, reliable and precise in operation. Also, the cam actuated adjustment mechanism may be sealed from liquid paper stock corrosion and other damaging paper making environment conditions. Cam follower pins attached to the foil support member move along sloped cam slots in a mounting base member when such support member is caused to slide along such base member to adjust the foil angle. The pins are attached to the foil support member so that they cannot drop off the foil apparatus and fall into the paper making machine to damage to such machine. In addition, the adjustable foil apparatus of the present invention is simple and compact so that it may be installed as a retrofit into existing paper making machines with minimum down time and minimum adjustment of the machine.
In addition, the cam follower pins are provided in the present invention as eccentric pins to allow for small adjustments of the foil height of the leading edge of the foil along the length of the foil to maintain the foil segment heights substantially constant for different foil angle positions. The cam follower pins may be of a ceramic coated metal for longer life to reduce wear when sliding in the cam slots of the cam actuated operating mechanism. Also, the drive mechanism for movement of the cam actuator slide which moves the foil support member can be achieved by hand rotation or motor driven rotation of the control shaft connected to such cam actuator. Since the foil support member is the only moving part during adjustment of the foil angle, this greatly simplifies the operation of the foil apparatus.